In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechaical system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that area from the solenoid to the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are spaced in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the recond media for a given amount of wire curvature.
In the wire matrix printer, the print head structure may be a multiple-element type with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner, while the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally-aligned single-element print heads which are caused to be moved in back-and-forth manner to print successive lines or dots in making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing. These single wire actuators or solenoids are generally tubular or cylindrically shaped and include a shell which encloses a coil, an armature and a resilient member arranged in manner and form wherein the actuator is operable to cause the print wire to be axially moved a small precise distance in dot matrix printing.
In the concept of dot matrix printing, it is generally desired to place the print element actuators in a position to allow characters to be printed in serial manner and this placement requires that the print wire or like print element actuators be very closely spaced with respect to each other. Since the print actuators are generally much larger in size than the diameter of the printed dot, a relatively long wire or like element must be provided to bring the desired print activity from its source, such as a moving armature or plunger or the like, to a vertical closely-spaced column arranged in a pattern such that the column of closely-spaced, tangentially coincident or overlapping dots will be produced on the record media if all actuators are fired or actuated at one time.
Representative documentation in the field of wire matrix print heads includes U.S. Pat. No. 3,828,908, issued to W. Schneider on Aug. 13, 1974, which discloses a print head having an armature that rests on a coil core and pivots in a groove of the coil yoke. A leaf spring is disposed between the armature and the core and one end of the spring is engaged with a printing needle.
U.S. Pat. No. 3,929,214, issued to D. G. Hebert on Dec. 30, 1975, discloses a wire matrix print head wherein armatures pivot about a fulcrum on the top edge of the outer coil pole, and a unitary connector positions the armatures and provides an O-ring reference surface for the ends thereof.
U.S. Pat. No. 3,994,381, issued to D. G. Hebert on Nov. 30, 1976, discloses an electromagnet assembly wherein the magnetic core and the magnetic yoke are secured to the mounting plate by a single nut. An armature retainer is adjustably attached to the yoke and at the hammer end of such retainer is a backstop or bumper which cushions the return shock of the armature back against the retainer, and spring bias means positions the armature in its non-energized position.
U.S. Pat. No. 4,051,941, issued to D. G. Hebert on Oct. 4, 1977, discloses an electromagnetic structure having a coil with inner and outer pole pieces and an armature along with a retainer for maintaining the armature engaged with the outer pole piece. The retainer is secured to a wire guide assembly and also a resilient member dampens the rebound force of each wire upon deenergization of the coil.
U.S. Pat. No. 4,060,161, issued to C. R. Nelson et al. on Nov. 29, 1977, discloses printing mechanism with armature shims spacing the armatures away from the magnet poles, and a unitary connector with arms for holding ends of the armatures.
U.S. Pat. No. 4,165,940, issued to C. T. Cacciola on Aug. 28, 1979, discloses a dot matrix print head that includes a leaf spring member with fingers for biasing the armatures to pivot on the outer pole.
U.S. Pat. No. 4,185,929, issued to D. G. Hebert on Jan. 29, 1980, discloses armatures biased against the inner pole by an O-ring on a pivot located outwardly from the O-ring.
U.S. Pat. No. 4,204,778, issued to Y. Miyazawa et al. on May 27, 1980, discloses a print head assembly with a spring with arms riveted to the armatures.
U.S. Pat. No. 4,230,038, issued to D. G. Hebert on Oct. 28, 1980, discloses a print head assembly with a plurality of armature members continuously engageable with a first O-ring at an intermediate portion of the members and a second O-ring for continuously engaging a radially outermost portion of the members. The second O-ring serves as a backstop for the armature members in printing operation.
U.S. Pat. No. 4,230,412, issued to D. G. Hebert on Oct. 28, 1980, discloses a print head assembly with a plurality of armature members, each having a drive head portion engaging an impact head portion of the print wire. In one embodiment an O-ring is placed between the drive head portion of the armature member and an adjustment hub member to support the drive head portion, and in another embodiment a flat annular member is used to support the drive head portion.
U.S. Pat. No. 4,244,658, issued to M. Mori on Jan. 13, 1981, discloses a first yoke with a coil frame fitted therein and a second yoke with a flat lever engaging a printing needle and wherein the flat lever is controlled by a suppress member.
U.S. Pat. No. 4,252,499, issued to Y. Miyazawa et al. on Feb. 24, 1981, discloses a printer head wherein the armatures are secured to a contilever spring near the fulcrum of the armatures.
U.S. Pat. No. 4,260,270, issued to P. G. Cavallari on Apr. 7, 1981, discloses a printing head wherein the armatures are placed on the outer magnetic core and biased by resilient string inserted in a groove of the armature retainer.
And, U.S. Pat. No. 4,273,452, issued to H. Honma on June 16, 1981, discloses a print head wherein the armatures are connected to the outer arm of the yoke with a deformation-preventing ring.